Apparatus for generating an electrical ignition current in a fuze of a projectile

ABSTRACT

An apparatus for generating an electrical ignition current in the fuze of a projectile to be fired from a weapon, comprising an induction coil arranged in the projectile, a magnet for generating a magnetic field, a bipartite yoke, one part of which is located at the projectile and the other part at the weapon barrel, for producing a change in the magnetic flux upon passage of the projectile through the weapon barrel. According to one embodiment the part of the yoke located at the weapon barrel comprises a number of ferromagnetic rings and paramagnetic rings arranged between the ferromagnetic rings. The part of the yoke located at the projectile body comprises a substantially cylindrical body member having a substantially disc-shaped flange for the reception of the induction coil as well as a soft iron disc. With this arrangement the magnet is a permanent magnet which is disposed between this cylindrical body member and the soft iron disc. The axis of the induction coil substantially coincides with the projectile axis, and the aforesaid ferromagnetic and paramagnetic rings are arranged at the end of the weapon barrel. It is possible, according to another embodiment, to use instead of a permanent magnet, an electromagnet located at the mouth of the weapon and containing such ferromagnetic and paramagnetic rings, with the yoke at the weapon barrel being in the form of a triple-arm yoke carrying two oppositely polarized electromagnetic coils.

BACKGROUND OF THE INVENTION

The present invention generally relates to weapon systems, and, morespecifically, concerns a new and improved construction of apparatus forgenerating an electrical ignition current in the fuze of a projectilewhich is intended to be fired from a weapon or gun. Generally speakingthe apparatus of this invention is of the type comprising an inductioncoil located in the projectile, a magnet for generating a magneticfield, a two-part or bipartite yoke, one part of which is located at theprojectile and the other part of which is located at the weapon barrel,in order to generate a change in the magnetic flux upon passage of theprojectile through the weapon barrel.

According to a state-of-the-art construction of apparatus of this type,as disclosed in U.S. Pat. No. 1,739,921, an electromagnet is arranged atthe mouth or muzzle of the weapon barrel and the projectile fuzepossesses an induction coil. Upon passage of the induction coil throughthe electromagnet there is induced a current in the induction coilwhich, on the one hand, is employed for charging a capacitor and, on theother hand, for switching-on a mechanical timing relay.

Disadvantageous with this prior art construction is the need to arrangean electromagnet at the muzzle at the region of the hot gases, andfurther, with such electromagnet there can only be induced a singlecurrent surge.

Furthermore, there is known to the art from U.S. Pat. No. 3,417,700 anapparatus where a number of induction coils containing permanent magnetsare uniformly distributed at the circumference or periphery of theprojectile body, and the coil axes are disposed radially with regard tothe projectile body. The magnetic field produced by the permanentmagnets is closed as long as the projectile is located within the weaponbarrel and opens as soon as the projectile departs from the weaponbarrel, resulting in a voltage being induced in the induction coil.

Yet this prior art apparatus is associated with the following drawbacks:

(a) such type arrangement of the induction coils cannot be employed withsmall caliber ammunition;

(b) the radial acceleration in the case of spinning ammunition does notallow for any such type arrangement of the induction coil; and

(c) there can only be generated a single pulse.

SUMMARY OF THE INVENTION

Therefore, with the foregoing in mind, it is a primary object of thepresent invention to provide an improved construction of apparatus forgenerating an electrical ignition current in the fuze of a projectile ina manner not associated with the aforementioned drawbacks andlimitations of the prior art proposals.

Another and more specific object of the present invention aims at theprovision of an apparatus of the previously mentioned type, by means ofwhich, during passage of the projectile through the barrel of theweapon, there can be generated as large as possible energy, and whichapparatus also is suitable for use with small caliber projectiles aswell as spinning ammunition or projectiles.

Now in order to implement these and still further objects of theinvention, which will become more readily apparent as the descriptionproceeds, the apparatus of this development is manifested by thefeatures that according to one embodiment:

(a) the part of the yoke located at the weapon barrel possesses a numberof ferromagnetic rings or ring members;

(b) paramagnetic rings or ring members are arranged between theferromagnetic rings;

(c) the part of the yoke located at the projectile body comprises asubstantially cylindrical body member having a substantially disc-shapedflange for the reception of the induction coil as well as a soft irondisc;

(d) the magnet in the form of a permanent magnet is arranged betweenthis substantially cylindrical body member and the soft iron disc;

(e) the axis of the induction coil substantially coincides with theprojectile axis; and

(f) the aforesaid ferromagnetic rings and paramagnetic rings arearranged at the end of the weapon barrel.

According to another embodiment of the invention, there is provided anarrangement wherein:

(a) the magnet comprises an electromagnet located at the mouth of theweapon barrel and composed of a number of ferromagnetic rings andparamagnetic rings arranged between the ferromagnetic rings;

(b) the part of the yoke at the weapon barrel comprises a three-arm yokeattached to said ferromagnetic rings;

(c) two electromagnetic coils polarized in opposite directions surroundat least part of said three-arm yoke; and

(d) the axis of the induction coil substantially coincides with the axisof the projectile.

An advantageous construction of the modified embodiment comprises threesuch ferromagnetic rings connected to one another by two of theparamagnetic rings which are in the form of sleeves.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and objects other than those setforth above, will become apparent when consideration is given to thefollowing detailed description thereof. Such description makes referenceto the annexed drawings wherein:

FIG. 1 is a longitudinal sectional view through an electronic projectilefuze arranged at the rear end of a projectile body equipped with agenerator;

FIG. 2 is a longitudinal sectional view through the front end of aweapon barrel having a muzzle brake;

FIG. 3 is a longitudinal sectional view through a second exemplaryembodiment of an electronic projectile fuze arranged at the rear end ofa projectile body equipped with a generator;

FIG. 4 is a longitudinal sectional view of a third exemplary embodimentof an ignition current generator;

FIG. 5 is a cross-sectional view taken substantially along the line V--Vof FIG. 4;

FIG. 6 schematically illustrates an exemplary embodiment of circuitrywhich can be used between the generator and capacitor with the apparatusof the invention;

FIG. 7 is a perspective view of the front end of a weapon barrel;

FIG. 8 is a longitudinal sectional view of a fourth exemplary embodimentof an electronic fuze arranged at the rear end of a projectile bodyequipped with an ignition current generator;

FIG. 9 is a diagram illustrating graphs of the magnetic flux and theinduced voltage; and

FIG. 10 is a fragmentary longitudinal sectional view through anelectronic fuze arranged at the rear end of a projectile body equippedwith an ignition current generator according to a fifth exemplaryembodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

At this point in the disclosure, it is mentioned that different ignitioncurrent generators for electronic projectile fuzes are known to the art,wherein both parts of the yoke are arranged in the projectile. With suchtype generators only the inertia forces can be utilized for generatingthe electrical energy.

In the case of spinning ammunition e.g. spinning projectiles, there canbe employed, for instance, rotary generators wherein the rotationalacceleration or a change in the moment of inertia can be utilized forgenerating the electrical energy. Friction forces appear between therotor and the stator, and difficulties arise during the mounting of therotor. Further, it is possible to use for spinning ammunition, forinstance surge generators. Depending upon the construction of such surgegenerators the mode of operation is different. There are requireddifferent safety devices, for instance for providing the necessarysafety during transport of the projectile.

In the case of fin-stabilized projectiles it is only possible to usesurge generators or batteries.

Piezoelectric generators can be employed both for spinning ammunition aswell as also for fin-stabilized projectiles. However, such typegenerators can only generate a very small amount of electrical energyper unit volume.

Now with the foregoing in mind the ignition current generators of theinvention have been designed for the purpose of avoiding a number ofsuch problems which are prevalent with the heretofore known prior artgenerators. Turning attention therefore initially to the embodimentshown in FIG. 1, it will be seen that a fuze housing 12 is attached atthe rear end of a projectile body 10 which contains an explosive charge11. This fuze housing 12 comprises a substantially pot-shaped threadedsleeve 13 and a tail screw 14 or equivalent structure which is threadedinto the internal threading 15 of the sleeve 13. This sleeve 13 is alsothreadably connected with the internal threading 16 of the projectilebody 10. Between the rear end surfaces or faces of the projectile body10 and the sleeve 13 on the one hand, and the head 14a of the tail screw14 on the other hand, there is arranged one part 17 of a yoke orequivalent structure. This yoke part 17 contains a permanent magnet ring18 and a soft iron disc 19 as well as an induction coil 20. Theinduction coil 20 is surrounded by an insulating ring 21. Further, aguide ring 24 is secured to the outer periphery or circumference of theprojectile body 10. Internally of the tail screw 14 there are locateddifferent components or elements of the fuze, which are not part of thesubject matter of the invention and can be constructed in conventionalfashion. One possible arrangement and operation of such elements,forming a fuze firing chain, has been disclosed for instance in thecommonly assigned U.S. Pat. No. 3,994,228, granted Nov. 30, 1976 listingas the inventor "Walter Hurlimann", and entitled "Projectile Fuze for aSpinning Projectile Containing a Detonator Cap and an Electro-MagneticFiring or Ignition Current Generator", to which reference may be readilyhad and the disclosure of which is incorporated herein by reference.Thus, in the description to follow there will only be considered enoughof the structure of the elements located within the tail screw 14 toprovide those skilled in the art with sufficient background informationand a clear appreciation of the underlining concepts of the presentinvention. Hence, it will be appreciated that belonging to such elementsis a charging capacitor 25 (see also FIG. 6) which can be charged by theinventive ignition current generator. Connected with the chargingcapacitor 25 is a detonator cap 26 which can be fired by the chargestored in the charging capacitor 25 as is well known. An electroniccontrol element 27 ensures for the proper detonation of the detonatorcap 26 at the correct moment in time. Located in front of the detonatorcap 26 is a detonator or transfer element 28 which transmits thedetonation or firing of the detonator cap 26 to a reinforcement charge29. This reinforcement charge 29 is attached to the sleeve 13 andprotrudes into the explosive charge 11. Further, the detonator 28 islocated in a rotor 30 which can be rotated out of the illustrated armedposition into a safety position. DDue to the spin of the projectile therotor 30 moves out of the safety position into the armed or firingposition.

Now as long as the projectile body 10 is located in the cartridge sleeve23, then the cartridge sleeve 23 short-circuits the magnetic fieldproduced by the permanent magnet 18. To ensure that the projectile canbe reliably fired or exploded at the target there is also provided animpact switch 31.

Continuing, and looking to the arrangement shown in FIG. 2, it will beseen that a muzzle brake 33 is attached to the front end of a weaponbarrel 32. Since this muzzle brake 33 does not constitute subject matterof the present invention, and its construction and mode of operation maybe assumed to be part of the state of the art and not important forunderstanding the teachings of the present invention, no furtherdiscussion thereof is believed to be necessary. At the inner wall of thesubstantially sleeve-shaped muzzle brake 33 there is arranged the secondpart of the aforementioned yoke, which second part has been generallydesigned by reference character 70. This yoke part 70 will be seen tocomprise rings or ring members 34 formed of a suitable paramagneticmaterial, for instance titanium. Now both between and in front of thesetitanium rings 34 there are secured the rings or ring members 35 formedof ferromagnetic material, for instance steel. The forwardmost ring 35is threaded into or otherwise appropriately secured at the muzzle brake33. The width of these rings is preferably somewhat greater than thewidth of the first part 17 of the yoke containing the soft iron disc 19(FIG. 1).

The mode of operation of the apparatus described and illustrated inFIGS. 1 and 2 is as follows: When, upon firing the projectile, theprojectile body or body member 10 departs from the cartridge sleeve 23,the magnetic field generated by the permanent magnet 18, and whichmagnetic field is located essentially at the yoke part 17, in the softiron disc 18 and at the neck of the cartridge sleeve 23, remainsshot-circuited by the weapon barrel 32. As soon as the projectile body10, together with the fuze attached to its rear end, flies through themuzzle brake 33, then the magnetic field is opened by the paramagneticrings 34 and is again short-circuited by the ferromagnetic rings 35.This opening and short-circuiting of the magnetic field in each caseinduces a voltage in the induction coil 20. Due to this induced voltagethe capacitor 25 which is connected with the induction coil 20 can becharged. The control element 27 ensures that the capacitor 25, after thecharging thereof, will not again discharge through the windings of theinduction coil, for instance by using diodes or equivalent structuressuitable for this purpose. Since during the movement of the projectilethe direction of the induced voltage changes, it is advantageous toemploy full wave rectifiers or a full wave rectifier arrangement, asgenerally indicated by reference character 75 in FIG. 6, at the controlelement 27.

At this point attention is directed to the modified version of fuzeillustrated in FIG. 3 which differs from that shown in FIG. 1essentially by the shape of the yoke part 17, the soft iron disc 19 andthrough the use of a suitable plastic ring 36.

The purpose of this modified version is especially seen in that thelarge forces, which are exerted by the propellent gas upon the tailscrew 14, are transmitted to the projectile body 10 in such a mannerthat the ignition current generator, especially the induction coil 20,is not damaged. In all other respects this construction of fuze is likethat considered above with regard to FIGS. 1 and 2, and therefore, thesame reference characters have been generally used for the same oranalagous components.

The ignition current generator depicted in FIGS. 4 and 5 will be seen tocomprise a two-part sector-shaped yoke 37 and 38 which is attached orotherwise intergrated with an essentially rectangular plate 39. Thisyoke or yoke part 37 and 38 is surrounded by an induction coil 40, whichin turn is arranged substantially coaxially with respect to thelengthwise axis of the projectile. At a second substantially rectangularplate 41 there is attached a permanent magnet 42, the shape of whichcorresponds to that of the yoke part or yoke 37, 38. The induction coil40 is surrounded by a suitable plastic mass 43.

The mode of operation of this embodiment of ignition current generatordoes not differ from the embodiments of ignition current generatorsillustrated and considered above with regard to FIGS. 1 and 3.

The construction of muzzle brake shown in perspective view in FIG. 7will be seen to comprise three ferromagnetic rings or ring members 44,45 and 46 which are interconnected with one another by two paramagneticsleeves or rings 47 and 48. The three ferromagnetic rings or ringmembers 44, 45 and 46 are further interconnected with one another by atriple-arm yoke or yoke part 49 formed of slightly magnetized material.This yoke part 49 is surrounded by two electromagnetic coils 50 and 51polarized in opposite directions, by means of which the threeferromagnetic rings 44, 45 and 46 can be magnetized in such a mannerthat, for instance, the intermediate ring 45 forms a north pole and theouter rings 44 and 46 south poles. As best seen by referring to FIG. 7,bores 52 or equivalent structure are provided in the paramagnetic rings47 and 48, and through such bores 52 there can escape the propellentgases. These bores 52 are directed such that they are effective inconventional manner as muzzle brakes.

Continuing, the projectile fuze shown in modified form in FIG. 8 merelydiffers from the construction of projectile fuze illustrated anddiscussed above in conjunction with FIG. 3 inasmuch as here there is notused any permanent magnet ring 18. This permanent magnet ring 18 isunnecessary if, as shown in FIG. 7, electromagnetic coils 50 and 51 areprovided at the muzzle brake. These electromagnetic coils 50 and 51together with the yoke part 49 and the three ferromagnetic rings 44, 45and 46 generate a magnetic field upon passage of the projectile throughthe muzzle brake i.e. through the rings 44, 45 and 46. This magneticfield induces voltage pulses in the induction coil 20 (FIG. 8) whichcause the capacitor 25 to charge.

The heretofore described embodiments of ignition current generatorspossess the following notable advantages:

The projectile does not contain any movable parts. A permanent magnet18, preferably formed of a cobalt-samarium-alloy, is either secured tothe yoke part 17 (FIGS. 1 and 3), or, electromagnets 50 and 51 areprovided at the muzzle brake (FIGS. 7 and 8).

There can be produced a number of surge pulses or voltage pulses, sincethere can be arranged in the barrel or in the muzzle brake a number offerromagnetic rings and a corresponding number of paramagnetic rings. Asa result, the charge stored in the capacitor 25 can be increased.

These ignition current generators operate independently of theprojectile spin and the firing acceleration. No inertia forces arerequired, rather there is utilized the relative movement between theweapon barrel and the projectile body for generating the charge.

The embodiments of ignition current generators disclosed herein areespecially suitable for use with small caliber ammunition and also canbe used with rockets where the firing acceleration and spin arerelatively small.

The ignition current generators constructed according to the inventiondo not require any appreciable change in the construction of the weaponor gun, rather it is only necessary to appropriately construct themuzzle brake.

Now by turning attention to FIG. 9 there will be recognized the courseof the magnetic flux Φ and the voltage. As soon as the yoke part 17together with the induction coil 20 as well as the permanent magnet 18and the soft iron disc 19 are located at the region of a paramagnetictitanium ring 34, then the magnetic flux Φ through the induction coil 20is small, as indicated by point 1 in the graph shown at the top portionof FIG. 9. As soon as the yoke part 17 together with the induction coil20 and the permanent magnet 18 and soft iron disc 19 are located at theregion of a ferromagnetic steel ring 35, then the magnetic flux Φthrough the induction coil 20 is large, as indicated by point 4 in thegraph at the upper part of FIG. 9. Since the induced voltage U_(i) isderived from the magnetic flux Φ, this voltage U_(i) assumes a negativevalue at point 4 upon decrease of the magnetic flux. The rectifierarrangement 75 of FIG. 6 ensures that the capacitor 25 also can becharged during the time that this alternating-current voltage isgenerated.

Finally, the projectile fuze illustrated in FIG. 10 differs from theheretofore described projectile fuze essentially by virtue of the factthat the generator will be seen to comprise in this case two inductioncoils 54 and 55. Between both of these induction coils 54 and 55 thereis arranged a permanent magnet ring 56 which can be radially magnetized.This permanent magnet ring 56 is mounted upon a yoke or yoke part 57which is formed by a sleeve 58 and two flanges 59 and 60.

The mode of operation of this modified version of generator is asfollows:

Upon passage of the projectile through the weapon barrel 32, there isfirst opened the magnetic field about the first induction coil 54 by theparamagnetic rings 34 (FIG. 2) and thereafter the magnetic field aboutthe second induction coil 55 is opened by the paramagnetic rings 34. Bymeans of the ferromagnetic rings 35 there is firstly again closed themagnetic field about the first induction coil 54 and thereafter there isclosed the magnetic field about the second induction coil 55 by theferromagnetic rings 35.

In the event that one of these two magnetic fields is open and the otheris closed, then the closed magnetic field ensures that the open magneticfield the magnetic flux Φ drops to null.

While there are shown and described present preferred embodiments of theinvention, it is to be distinctly understood that the invention is notlimited thereto, but may be otherwise variously embodied and practicedwithin the scope of the following claims. Accordingly,

What we claim is:
 1. An apparatus for generating an electric ingnitioncurrent in a fuze of a projectile intended to be fired out of the barrelof a weapon, comprising:an induction coil located in the projectile; amagnet for generating a magnetic field; a two-part yoke, one part ofwhich is located at the projectile and the other part at the weaponbarrel, in order to produce a change in the magnetic flux upon passageof the projectile through the weapon barrel; the part of the yokelocated at the weapon barrel comprises:a number of ferromagnetic rings;and paramagnetic rings arranged between the ferromagnetic rings; thepart of the yoke located at the projectile comprises:a substantiallycylindrical body member having a substantially disc-shaped flange forthe reception of the induction coil; and a soft iron disc; said magnetcomprising a permanent magnet arranged between said substantiallycylindrical body member and said soft iron disc; the axis of theinduction coil substantially coinciding with the axis of the projectile;and said ferromagnetic rings and paramagnetic rings are arranged at theend of the weapon barrel.
 2. The apparatus as defined in claim 1,further including:a muzzle brake provided for the weapon barrel; saidferromagnetic rings and paramagnetic rings being arranged at said muzzlebrake of the weapon barrel.
 3. The apparatus as defined in claim 1,wherein:said permanent magnet arranged at the projectile is formed of acobalt-samarium-alloy.
 4. An apparatus for generating an electricignition current in a fuze of a projectile intended to be fired out ofthe barrel of a weapon having a barrel mouth, comprising:an inductioncoil located in the projectile; a magnet for generating a magneticfield; a two-part yoke, one part of which is located at the projectileand the other part at the weapon barrel, in order to produce a change inthe magnetic flux upon passage of the projectile through the weaponbarrel; said magnet comprising an electromagnet located at the mouth ofthe weapon barrel and composed of a number of ferromagnetic rings andparamagnetic rings arranged between the ferromagnetic rings; the part ofthe yoke at the weapon barrel comprising a three-arm yoke attached tosaid ferromagnetic rings; two electromagnetic coils polarized inopposite directions surrounding at least part of said three-arm yoke;the axis of the induction coil substantially coninciding with the axisof the projectile.
 5. The apparatus as defined in claim 4, wherein:saidnumber of ferromagnetic rings comprises three ferromagnetic ringsconnected to one another by two of said paramagnetic rings in the formof sleeves.
 6. An apparatus for generating an electric ignition currentin a fuze of a projectile intended to be fired out of the barrel of aweapon, comprising:an induction coil located in the projectile; a magnetfor generating a magnetic field; a two-part yoke, one part of which islocated at the projectile and the other part at the weapon barrel, inorder to produce a change in the magnetic flux upon passage of theprojectile through the weapon barrel; the part of the yoke located atthe weapon barrel comprises:a number of ferromagnetic rings; andparamagnetic rings arranged between the ferromagnetic rings; the part ofthe yoke located at the projectile comprises:a substantially cylindricalbody member having a substantially disc-shaped flange for the receptionof the induction coil; and a soft iron disc; the axis of the inductioncoil substantially coinciding with the axis of the projectile; and saidferromagnetic rings and paramagnetic rings are arranged at the end ofthe weapon barrel.